Molecular Systematics of the Trilliaceae sensu lato as Inferred from rbcL Sequence Data

Abstract

In this paper, we examine the phylogenetic affinities of Trilliaceae sensu late. DNA sequences of the rbcL gene were analyzed for 8 species from Trilliaceae sensu lato ( Trillium kamtschaticum, T. sessile, Daiswa polyphylla, Kinugasa japonica, Paris tetraphylla, Scoliopus bigelovii, S. hallii, and Medeola virginiana) and 10 other species from Liliaceae sensu lato. The analysis indicates that Trilliaceae sensu stricto ( Trillium, Daiswa, Kinugasa, and Paris) is monophyletic and that Trilliaceae sensu lato is not monophyletic. Scoliopus and Medeola do not form a clade with Trilliaceae sensu stricto. Instead, they form a clade with Uvulariaceae and Liliaceae sensu stricto, respectively. Relative to the rbcL genes of Trilliaceae sensu stricto, Scoliopus and Medeola displayed approximately 14-24 synonymous substitutions per 100 sites. In similar comparisons with Streptopus and Clintonia (Uvulariaceae), these displayed approximately 1-4 synonymous substitutions per 100 sites. The rbcL gene analysis supports the previous suggestion that Scoliopus and Medeola should be moved from Trilliaceae to Liliaceae sensu stricto. The analysis also indicated that Veratrum (Melanthiaceae) may be related to Trilliaceae sensu stricto. For reconstructing the phylogeny of lower taxonomic level as such, it was found that data on nonsynonymous base substitution as well as weighting in the first and second positions of codons are not useful.